Correct use of POTCAR files

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Correct use of POTCAR files

Postby mikhail » Mon May 30, 2016 2:58 pm

Hello!
I have two questions concerning the use of POTCAR file.

1) I wish to perform calculations with rPBE functional. As written in VASP manual the xc functional is specified in the POTCAR file. But among all available POTCAR files only files with Ceperley-Alder(LDA), PW91, and PBE exist. I did not find a POTCAR with rPBE functional specified in it. So I see the only way to perform such a calculation by using a POTCAR generated for LDA and specify the variable GGA=RP in the INCAR file. But when I perform such a calculation the following message appears in the OUTCAR file:

| You enforced a specific xc-type in the INCAR file, |
| a different type was found on the POTCAR file |
| I HOPE YOU KNOW, WHAT YOU ARE DOING


So I am not sure if the way I do the calculation is correct.
The question is whether the way I do the calculations is correct?
If not, what is the rihgt way to perform the calculation with rPBE functional


2)I have seen that some new POTCAR files have been created. I mean precisely potpaw_LDA.52 and potpaw_PBE.52 . What is the difference between these files and the old versions of PAW LDA and PBE files. Which of them should be used in the calculations?
mikhail
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Re: Correct use of POTCAR files

Postby admin » Tue May 31, 2016 12:53 pm

There are two versions of revised PBE (cf. the comparison of functionals in J.Chem.Phys.132(2010)164117.
revPBE (PRL1980(1998)890) and RPBE (PRB59(1999)7413). The installation in VASP corresponds to RPBE.
The revision is an attempt to improve the PBE functional. Therefore the correct way is to take POTPAW_PBE
and use GGA = RP . The message in OUTCAR only confirms that you are changing the xc-part of the functional
from PBE to RPBE.
POTPAW_PBE.52 is a new generation of the pseudopotential with kinetic energy density evaluated for
the use e.g. in meta-GGAs.
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Re: Correct use of POTCAR files

Postby mikhail » Wed Jun 01, 2016 12:02 pm

Okay. Thank you for the detailed answer.
I will see the mentionned papers.
Perhaps I will have one or two small questions afterwards.
Thanks again.
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